Investigating the Role of Cellular Signaling in Liver-Stage Malaria Infection

描述(申请人提供)：疟疾是一个严重的健康负担，特别是在发展中国家，但目前还没有疫苗可用。寄生虫通过雌性按蚊的叮咬进入人类宿主，首先感染肝细胞，然后转移到导致所有疾病的血液感染。在肝脏发育阶段，寄生虫通过防止感染细胞的程序性细胞死亡(凋亡)来保护它们在宿主肝细胞中的家园。基因减毒寄生虫(GAP)株可诱导小鼠无菌免疫，其中一株已被证明不能控制宿主细胞的凋亡。然而，野生型寄生虫抑制细胞凋亡的机制尚不清楚。我将首先使用各种表型分析来全面描述感染野生型寄生虫和GAP的肝细胞的凋亡表型。下一步，我计划监测肝细胞中一些候选信号蛋白对野生型和GAP感染的反应。这将使我们能够识别差异激活的候选基因，以响应促凋亡的减毒寄生虫和抗凋亡的野生型寄生虫。最后，我建议使用细胞培养模型以及在小鼠身上进行免疫和挑战实验来进一步研究差异调控的候选基因。这项研究将导致发现对野生型寄生虫抑制细胞凋亡起关键作用的肝细胞蛋白。由于感染的凋亡细胞比存活细胞对免疫系统有更好的刺激作用，抑制这些宿主蛋白可能会导致野生型寄生虫诱导凋亡，也可能增强减毒活疫苗诱导的免疫力。改变肝细胞对感染的反应可以将促进疾病的野生型寄生虫转变为增强保护性免疫的寄生虫，从而可能在疟疾感染的早期阶段提供新的干预策略。

DESCRIPTION (provided by applicant): Malaria presents a severe health burden, particularly in the developing world yet no vaccine is currently available. The parasites enter the human host through the bite of the female Anopheles mosquito and first infect liver hepatocytes, before moving to the blood infection that causes all disease. During liver stage development, parasites protect their home in the host hepatocyte by preventing programmed cell death (apoptosis) of the infected cell. Genetically attenuated parasite (GAP) strains that induce sterile immunity in mice have been developed, and it was shown for one of these strains that it cannot control host cell apoptosis. The mechanism of the inhibition of apoptosis by wildtype parasites, however, has not been elucidated. I will first fully delineate the apoptotic phenotype of hepatocytes infected with wildtype parasites and GAPs using a variety of phenotypic assays. Next, I plan to monitor a number of candidate signaling proteins in hepatocytes in response to both wildtype and GAP infections. This will allow us to identify candidate genes that are differentially activated in response to pro-apoptotic attenuated parasites and anti-apoptotic wildtype parasites. Finally, I propose to further investigate candidate genes that are differentially regulated using a cell culture model, as well as immunization and challenge experiments in mice. This study will lead to the discovery of hepatocyte proteins critical to modulating the inhibition of apoptosis by wildtype parasites. Since infected apoptotic cells are a better stimulus for the immune system than surviving cells, inhibiting these host proteins may cause the induction of apoptosis by wildtype parasites and might also enhance immunity induced by live-attenuated vaccines. Altering the hepatocyte response to infection could convert a wildtype, disease promoting parasite into one that promotes protective immunity and might thus inform new intervention strategies at the early stage of malaria infection.